Friday, July 16, 2010

Danaus plexippus

Another local species! And an arthropod to boot! How lucky you are!

This is the caterpillar of the monarch butterfly, known for its relatively long migrations across parts of North and Central America. However, unlike migratory bird species, the adults do not return to their original homes. The children or grandchildren will return to the homes of their ancestors, however. This is because cyclically, four generations of monarchs do not survive longer than a few weeks. How the progeny can find “home” is still subject to research. Perhaps they are following the sun, magnetic fields or geographic landmarks. This puzzle has prompted a project (alliteration!) called “Monarch Watch” which encourages hobbyist naturalists to record and report their sightings of these butterflies. You can visit their website here.

These butterflies and their migration patterns are considered threatened, mostly due to habitat loss and efforts by both the US and Mexican governments are underway to protect their habitats.

Their eggs are laid on plants in the Asclepiadaceae milkweed family. By processing certain compounds found in milkweeds they are given an unpalatable taste or even toxicity to their predators. Like most toxic insects both the larvae and the adults are brightly colored to warn of their poisons. Being poisonous doesn’t do very much good if your predators don’t know you’re poisonous.

Oh, a natural history factoid just popped into my head. There is a distinction between poisonous and venomous: poisonous animals are ones like our friend the monarch here which deliver toxins when eaten. That is, toxins are stored or produced within the organism. Venomous animals introduce toxins directly into their targets, often with a bite or sting. So lionfish, rattlesnakes, and wasps are all venomous animals. Ah, how I love distinctions.


EOL (again):

Great Plains Nature Center, Wichita KS:

Monarch Butterfly Website:

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